Checking brake system

First, let me say that I am currently driving locally. I now have the distinct impression that my company is not doing any visual checks of the braking system during scheduled maintenance services. The questions are:
. 1. What should I, as a concerned driver, be looking at?
. 2. How would I recognize the problem when I am looking at them?
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Apparently, since I am no mechanic, I need the step by step idiots guide to the driver's check of the braking system. I hope I am the only person who does not get it. But, I am posting this thread in the Newbie section just in case someone else may need to know this type of information. Thank you for any information you can give me.

 

Truck is a class B straight Mack trash truck that was involved in a rear end accident. Brakes were stopping the vehicle well enough during normal braking on Interstate and local roads in morning rush hour traffic. First time I had to go hard on the brakes --- nothing. Immediately after the rearend accident, I called for road maintenance. Mechanic found brakes out of adjustment, one slack adjuster barely functioning and something about the S cam that I didn't quite understand. He adjusted the brakes. I have a copy of the maintenance write up. Shortly after that, truck was returned to the terminal shop.
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Now this company has a really well deserved reputation for being really cheap. Yet they replaced the brake drums, brake linings, slack adjusters, S cams and their associated bushings on both sides of both drive axles. And yes I have a copy of this maintenance write up that describes all the work and parts that were replaced as well. Company says they did all this work because they don't want any problems with this truck. HUH??? They replace all these parts just for the fun of it? I think not.
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I may be ugly but I ain't stupid. IF visual inspections were done during PM's why did brakes fail under hard braking? Why are they replacing all these parts? Come on; this just does not pass the smell test.